When we were younger, my brother and I had a game of ‘brother-proofing’ each others cards; this consisted of covering the envelope with as much tape as we could before we were told off for wasting it. This year I decided to revive this game; on Christmas day I presented my brother with his card:
Inside which was an envelope that I had constructed from sheet steel:
I had welded the seams with my MOT welder; even with a current limiting stage added, I still had trouble welding such thin steel (it came from the side of an old fridge and is about 1mm thick mild steel as far as I can tell).
Then gave up and disappeared to the garage, from where the sound of the angle grinder was evident. This exposed the envelope; although difficult to tell from this photo, it was brother-proofed in the classic style with several layers of sellotape.